LONDON (Reuters) - RSA underwriting profit rose strongly for the year to date but net written premiums were flat after the British insurer cut poorly performing parts of its business, it said on Thursday, sending its shares higher. Best known in Britain for its "More Than" brand, RSA also has major businesses in Canada, Ireland and Scandinavia.The home, motor and commercial insurer warned last year about the poor performance of its London-based international commercial insurance business and..